Continuously adjustable transmission

ABSTRACT

A continuously adjustable transmission comprises a number of arms (18), one end of each of which is pivotably connected to a rotatably arranged driven first member (17) and of which the other end cooperates with a second rotatably arranged member (15). The axes of rotation (20) of the arms (18) are parallel to the axes of rotation of the members (15, 17) and are evenly distributed about a circle. The part of the second member (15) acted upon by the arms lies at a radial distance from the circle in which the axes of rotation (20) of the arms (18) are situated. Both members (15, 17) are movable in relation to each other between a concentric position in which the transmission ratio is 1:1 and an eccentric position for obtaining another transmission ratio. The arms (18) are situated in a common radial plane and the end of each arm which cooperates with the second member (15) has an elongated clamping member (19) pivotably connected with the arm (18) through an axially extending shaft (21). Each clamping member (19) is accommodated in a ring-shaped slot (22) in the second member (15). A spring (24) acts between each arm and the corresponding clamping member (19) in a direction such that opposite ends of the clamping member (19) will be urged to engage two opposite, substantially cylindrical walls (23) of the slot (22). The distance between the points where one clamping member (19) engages the opposite walls (23) is greater than the radial distance between the walls (23).

The invention relates to a continuously adjustable transmission, whichcomprises a number of arms, one end of which is pivotably connected to arotatably arranged first member to be driven from the outside or by thetransmission itself, and of which the other end acts on a secondrotatably arranged member, the axes of rotation of the arms beingparallel to the axes of rotation of the members and being evenlydistributed about a circle, in which the part of the second member beingacted upon by the arms lies at a radial distance from the circle onwhich the axes of rotation of the arms are situated, both members havingbeen arranged such that they are movable in relation to each otherbetween a concentric position in which the transmission ratio is 1:1 andan eccentric position for obtaining another transmission ratio.

Such a transmission is known from NL-A-8900501. In this known device,the arms are also pivotably connected to the second member and executedtelescopically for being able to accommodate the differences in lengthoccurring in the eccentric position of both members. Only when they havetheir minimal lengths, they will be active for transmission of forces.Further, each arm with its related parts is situated in a separateplane, so that the transmission takes up a lot of space and comprisesmany parts.

The invention intends to remove these disadvantages and to that endprovides that a number of arms are situated in a same radial plane andthat each of the arm-ends acting on the second member has at the endconcerned been provided with an elongated clamping member rotatablyconnected with the arm through an axially extending shaft, whichclamping member has been accommodated in a ring-shaped slot made in thesecond member, with parts of the clamping member engaging the twoopposite, substantially cylindrical walls of the slot by means of springforce, while the center of rotation between a clamping member and thecorresponding arm is positioned such and the clamping member is formedsuch, that under certain conditions, the clamping member establishes afixed connection between the arm and the second member, as a result ofclamping.

The spring force exerted on a clamping member need only be sufficientfor keeping the parts concerned of the clamping member in contact withthe walls of the slot and therefore can be small. When the clampingmember is not active, it will easily slide along the walls of the slot,which only produce a small frictional resistance.

For a most suitable distribution of forces exerted on the various partsit can be provided that the clamping member extends at both sides of thecorresponding arm and that each of the parts present at both sides ofthe arm is situated in a slot of the second member.

Through this it is achieved, that the arm is only under tension orpressure and that only a radially directed force is exerted on theclamping member.

In order to obtain a still better clamping of a clamping member in theslot of the second member, it can be provided that at least one of thewalls of the slot, seen in cross section, has a V-shape such that theclamping member is accommodated in the V-shaped part.

According to a development of the invention, the spring force by whichthe clamping member engages the walls of the slot, can be created bymeans of a tension or compression spring situated between the clampingmember and the corresponding arm.

Owing to the fact, that the arm and the clamping member at atransmission ratio other than 1:1 will take up a continually varyingposition in relation to each other, the spring force will likewisechange continuously.

When this would cause difficulties, it can be provided that the clampingmember consists of two sections, with the one section near one end beingpivotally connected to the arm and near the other end to the othersection, in which the pivoting point between the sections is situatedbetween the walls of the slot and a spring is present between thesections for pressing each of the sections against the correspondingwall of the slot, while the end of the arm connected with one section isguided by a part of the second member, which is concentric to the slotpresent in this member.

It can also be provided that the spring force is supplied by a memberarranged such, that only in a certain position of the clamping member inrelation to an arm or arms, a spring force is exerted on the clampingmember.

This can be achieved for example by applying a compression spring, whichwill deflect on exceeding a certain force and therefore will hardlyproduce any force.

The invention is further explained by way of embodiments, illustrated inthe drawings in which:

FIG. 1 shows a section across the axis of a device according to theinvention, applied in a bicycle wheel;

FIG. 2 shows a section according to line II--II of FIG. 1;

FIG. 3 diagrammatically shows a section across a part of the device ofthe FIGS. 1 and 2;

FIG. 4 shows a side view of the parts of FIG. 3;

FIG. 5 shows a section across the slot of an alternative shape;

FIG. 6 shows a section across a clamping member extending at both sidesof the arm and accommodated in two slots;

FIG. 7 diagrammatically shows a view of a slot with a number of clampingmembers and the corresponding arms in the position in which thetransmission ratio is 1:1;

FIG. 8 shows a view corresponding to FIG. 7, yet in the position inwhich the transmission ratio has been changed; and

FIGS. 9 and 10 diagrammatically show views corresponding to FIG. 4, yetof other embodiments of the clamping member.

FIGS. 1 and 2 show a continuously adjustable transmission 1 mounted inthe hub 2 of a bicycle wheel 3, the other parts of which, namely thespokes and with the rim, have been omitted.

The wheel 3 is rotatably mounted on the shaft 4 by means of the bearings5 and 6 and the shaft 4 is fixed in the fork 7 by nuts with washers notfurther indicated.

Beside the bearing 6, the shaft 4 is provided with a portion 8, which iseccentric to the axis 9 of the shaft 4. A bushing 10 is rotatablymounted on the portion 8 by means of an eccentric bore 11. The bush 10is rotatable by means of the part 12 fixedly connected thereto, aroundwhich e.g. a cable not further described can extend for adjusting theposition of the bushing 10 in respect of the axis 9. On the bushing 10,the bearings 13 and 14 are situated for rotatably supporting the part15. The part 15 can be driven by means of the sprocket wheel 16. Byrotation of the bushing 10, the axis of the bearings 13 and 14 cancoincide with the axis 9 of the shaft 4, or be at some distancetherefrom, as appears in particular from FIG. 2.

The part 17 is connected to the hub 2 and the arms 18 and the clampingmembers 19 are situated between the parts 15 and 17. The arms 18 arepivotably connected to the part 17 by means of the pins 20, and aclamping member 19 is connected to each arm 18 by means of a pin 21. Theclamping members 19 are situated in slots 22 in the part 15. Thecylindrical walls of the slots are indicated by 23.

For a better understanding of the invention, FIGS. 3 and 4diagrammatically show an arm 18, which is rotatably connected with thepart 15 by the pin 20 and by the pin 21 to the clamping member 19. Theclamping member 19 is in the slot 22 of the part 17, such that it willclamp itself against the walls 23 of the slot 22 upon a certain movementof the arm 18. Between the arm 18 and the clamping member 19 is a spring24 for keeping the clamping member in engagement with the walls 23 alsowhen it is not clamped tightly in the slot 22.

FIG. 5 shows the possibility that both walls 23 of the slot 22 are notformed cylindrically, but in V-shape. It is also possible, that only oneof the walls is formed as such, depending on the shape of the clampingmember 19.

FIG. 6 shows a clamping member 19 formed as an entity mounted to one arm18 and cooperating with two slots 22.

FIGS. 7 and 8 diagrammatically show the operation of the transmissionaccording to the invention. In FIG. 7, the axis of rotation of the part15, driven by the sprocket wheel 16 for example, is in line with that ofthe wheel hub 2, so that an entirely rotation-symmetrical arrangement ofthe arms 18 and the clamping members 19 is obtained. All clampingmembers can then be operative for transmitting the rotational force fromthe sprocket wheel 16 to the wheel hub 2. In FIG. 8, the axes ofrotation are displaced in relation to each other by rotation of thebushing 10. Due to this, only one of the arms 18 will effect theclamping of the clamping member 19 connected therewith to the slot 22,and the slot 22 will thereby be moved over a different distance than inthe case of FIG. 7 and thus will get a different peripheral velocity.The speed of the part 15 provided with the slot 22 will therefore bedifferent from that of the part 17. The other clamping members 18 willslide along the walls 23 of the slot 22 and not be able to clampthemselves therein.

The arrow P roughly indicates the area in which a certain clampingmember is operative. As it appears, here the clamping members 19together and in relation to the corresponding arms 18 take up adifferent position than is the case with the arms lying further away.This situation can be used to ensure, that the non-operative clampingmembers are not or are hardly pressed against the walls of the slot. Asmentioned above, one can employ a compression spring for example, whichdeflects on exceeding a certain force.

FIG. 9 shows another specific embodiment of a clamping member 19. It hason the one hand a collar 24 with one straight shoulder, that can lieagainst the one wall 23 of the slot 22, while the other end of theclamping member 19 is rounded off in order to lie against the other wall23. The spring 24 is again mounted between the illustrated arm and theclamping member 19.

FIG. 10 shows the possibility of guiding the end of the arm 18 connectedto the clamping member 19 into a slot 25, for example by means of thepivot pin 21. The clamping member 19 now comprises two sections 26,pivotally connected to each other by the pin 27 and loaded by the spring24 in such a way, that they will be in line as much as possible.

In the figures, it is illustrated that all arms 18 are in one singleplane. Owing to this, the number of arms that can be used with a certaindiameter of the parts will be limited. When one arm becomes inoperativeand the next arm becomes operative, a certain changing of load willoccur. In most cases, this will not cause any difficulties and be hardlynoticeable. However, when said changing of load is undesired, there isthe possibility of mounting a number of arms in two planes lyingadjacent each other, such that the arms of the one system are situatedbetween the arms of the other system, by which the transmission of forcebecomes more even.

It will be obvious, that only some possible embodiments have beenillustrated in the drawing and described above and that many changes canbe made without departing from the scope of the appended claims.

I claim:
 1. In a continuously adjustable transmission, which comprises anumber of arms (18), one end of each of which is pivotably connected toa rotatably arranged driven first member (17) and of which the other endis operatively connected to a second rotatably arranged member (15), theaxes of rotation (20) of the arms (18) being parallel to the axes ofrotation of the members (15, 17) and being evenly distributed about acircle, in which the part of the second member (15) acted upon by thearms lies at a radial distance from the circle in which the axes ofrotation (20) of the arms (18) are situated, both members (15, 17) beingmovable in relation to each other between a concentric position in whichthe transmission ratio is 1:1 and an eccentric position for obtaininganother transmission ratio; the improvement wherein said arms (18) aresituated in a common radial plane and the end of each arm which isoperatively connected to the second member (15) having an elongatedclamping member (19) pivotably connected with the arm (18) through anaxially extending shaft (21), said clamping member (19) beingaccommodated in a ring-shaped slot (22) in the second member (15), andspring means (24) acting between each arm and the corresponding saidclamping member (19) in a direction such that opposite ends of theclamping member (19) will engage two opposite, substantially cylindricalwalls (23) of the slot (22).
 2. Transmission according to claim 1,wherein the clamping member (19) extends on both axial sides of thecorresponding arm (18) and each of the parts present on both axial sidesof the arm is situated in a slot (22) of the second member (15). 3.Transmission according to claim 1, wherein at least one of the walls(23) of the slot (22), seen in cross section, has a V-shape such thatthe clamping member (19) is accommodated in the V-shaped part. 4.Transmission according to claim 1, wherein the clamping member (19)consists of two sections (26), with the one section near one end beingpivotally (21) connected to the arm (18) and near the other end to theother section, and wherein the pivoting point (27) between the sections(26) is situated between the walls (23) of the slot (22) and said springmeans (24) is present between the sections (26) for making each of thesections engage the corresponding wall (23) of the slot (22), while theend of the arm (18) connected with one section is guided by a part ofthe second member (15), which is concentric to the slot (22) present inthis member.